PWM output on a PIC

[ALPHA4390]

I am trying to get a working example of PWM on a 33EP256MU806 pic.

I am not having much success as the help in the compiler does not give a very good description of the PWM functions.

setup_compare(1, COMPARE_PWM_EDGE | COMPARE_TIMER2);

I am getting this error and i haven't a clue how to find out whats wrong

*** Error 108 "PWM_Edge_AlignedT.c" Line 28(39,54): Invalid parameters to built in function :: Invalid Pin

Any help is welcomed

[jeremiah]

99% of the time "invalid pin" errors are from lack of using #pin_select. If your chip needs pin select for the PWM, then you need to use that before calling setup_compare. That said, at first glance yours shouldn't need that, so this may be a case where CCS missed it and needs to make corrections. Study the datasheet and if they indeed implemented this wrong, let them know via email.

For workarounds you can access the registers directly.

[Ttelmah]

Deep breath.

It is the #PIN_SELECT.

Key is that this chip has two different ways of actually generating a PWM. You can generate a PWM, on any of the PPS pins using output compare (which is what is being tried). This comes out on the OCx pins, and these are PPS pins (so must be selected to the required pin before use).

So:
#PIN_SELECT OC1=PIN_yy

The command will then be accepted.
This is the standard DsPIC PWM.

However this chip also has a separate high speed PWM module. This allows configuration designed for things like motor control etc. This outputs on the PWMxH & PWMxL pins, which are predefined. This module is controlled by the hspwm functions.

setup_hspwm_unit(), set_hspwm_phase(), set_hspwm_duty(), &
set_hspwm_event()

So for a simple PWM, the current function is the way to go, but this requires a #PIN_SELECT. Alternatively use the hspwm functions.

[ALPHA4390]

Thanks for the quick response,

I searched all of the examples and could not find reference to #PIN_SELECT OC1=PIN_yy, I even have the embedded C book with PWM examples that did not refer to #PIN_SELECT OC1=PIN_yy.

I assume the defined pin must be a CCP PWM pin? As i have defined a general io pin for a quick test on the dev board and it looks like i can only get 50% duty cycle.

[temtronic]

I don't use that PIC or have the compiler for it but you should be able to search the CCS manual for syntax and use of it.
Mr T is trying to lead you to what must be done.
BTW this is a CCS specific item and will NOT be covered in a general C text.


Jay

[Ttelmah]

With CCS, you need to be using several layers of data:

1) General C book (for the syntax of C operations).
You will not find chip specific or CCS specific functions here.
2) CCS's manual (for the list of their functions and syntax).
3) The chip's data sheet (what features the chip has).
4) The include file for the processor. This will tell you which 'extra' functions this chip has, and the values they can use.
5) The examples

First key one here is the chip's data sheet.
PPS, is peripheral pin select. Section 11/4. This is a specific feature of the later PIC's, that allows certain peripherals to be connected to any PPS pin.

If you look at the data sheet, there are tables for the output peripherals and input peripherals, listing for each whether it is a fixed peripheral, or a PPS peripheral.
Tables 11-1, 11-2 & 11-3
These show what peripherals/pins can be mapped.

Then if you open the header file for the PIC, after it's initial section (fuses etc.), there is a section listing all the peripheral names that CCS uses for the devices that can (must) be mapped, and all the pin names they can be mapped to.
This section starts with the line:
// #pin_select function=pin

So, telling you how it is used to map a function to a pin.

No. This PWM output, has nothing to do with the PWMx pins.
As already said, the PWMx pins are the fixed pins for the HSPWM peripheral.

How the selection works, is shown in the CCS examples.

If you look at
EX_Pinselect.c
EX_pinselect2.c

These show the generic way the pin select function works.